Problem reading Serial Port C#.net 2.0 to get Weighing machine output - windows-xp

Question

I'm trying to read weight from Sartorius Weighing Scale model No BS2202S using the following code in C#.net 2.0 on a Windows XP machine:
public string readWeight()
{
string lastError = "";
string weightData = "";
SerialPort port = new SerialPort();
port.PortName = "COM1";
port.BaudRate = 9600;
port.Parity = Parity.Even;
port.DataBits = 7;
port.StopBits = StopBits.One;
port.Handshake = Handshake.RequestToSend;
try {
port.Open();
weightData = port.ReadExisting();
if(weightData == null || weightData.Length == 0) {
lastError = "Unable to read weight. The data returned form weighing machine is empty or null.";
return lastError;
}
}
catch(TimeoutException) {
lastError = "Operation timed out while reading weight";
return lastError;
}
catch(Exception ex) {
lastError = "The following exception occurred while reading data." + Environment.NewLine + ex.Message;
return lastError;
}
finally {
if(port.IsOpen == true) {
port.Close();
port.Dispose();
}
}
return weightData;
}
I'm able to read the weight using Hyperterminal application (supplied with Windows XP) with the same serial port parameters given above for opening the port. But from the above code snippet, I can open the port and each time it is returning empty data.
I tried opening port using the code given this Stack Overflow thread, still it returns empty data.
Kindly assist me.

Answer 1

I know this is probably old now ... but for future reference ...
Look at the handshaking. There is both hardware handshaking and software handshaking. Your problem could be either - so you need to try both.
For hardware handshaking you can try:
mySerialPort.DtrEnable = True
mySerialPort.RtsEnable = True
Note that
mySerialPort.Handshake = Handshake.RequestToSend
I do not think sets the DTR line which some serial devices might require
Software handshaking is also known as XON/XOFF and can be set with
mySerialPort.Handshake = Handshake.XOnXOff
OR
mySerialPort.Handshake = Handshake.RequestToSendXOnXOff
You may still need to enable DTR
When all else fails - dont forget to check all of these combinations of handshaking.

Answer 2

Since someone else will probably have trouble with this in the future, hand shaking is a selectable option.
In most of the balances you will see the options for Software, Hardware 2 char, Hardware 1 char. The default setting for the Sartorius balances is Hardware 2 Char. I usually recommend changing to Software.
Also if it stops working all together it can often be fixed by defaulting the unit using the 9 1 1 parameter. And then resetting the communication settings.
An example of how to change the settings can be found on the manual on this page:
http://www.dataweigh.com/products/sartorius/cpa-analytical-balances/